Abstract

We study the final energy distribution of a slow cesium atomic beam, after its reflection on a mirror formed by a laser evanescent wave. For a sinusoidal modulation of the mirror height at frequency Ω, sidebands appear in this energy spectrum, corresponding to a transfer of energy ±nhΩ, where n is an integer. This is a signature of a phase modulation of the atomic de Broglie wave [1]. We have also chopped this atomic beam by switching on the mirror for only a very short period of time. We have shown that the outcoming energy distribution is broadened according to the time-energy uncertainty relation. To our knowledge, this is the first observation, for matter waves, of the phenomenon of diffraction by a time slit [2]. Finally we have used the temporally diffracted beam to design a Young-slit like interferometer in which the interferring paths consist of atomic trajectories bouncing at various times.

© 1996 IEEE